To illustrate the means by which newly generated lung mediators can affect allergic inflammation, investigators have shown that inhaled allergen is associated with enhanced bone marrow generation of eosinophils. This enhanced bone marrow production of eosinophils is associated with bone marrow cell generation of IL-5, which causes terminal differentiation of eosinophils and their release into the circulation. Presumably, these recently generated eosinophils enter the circulation and are recruited to the lung where they may further the development of eosinophilic inflammation and the severity of asthma.